US regulators formally approve the single-shot Johnson & Johnson COVID-19 vaccine

US regulators have formally approved the single-shot Johnson & Johnson COVID-19 vaccine, the third jab to be authorised in the country.

The vaccine is set to be a cost-effective alternative to the Pfizer and Moderna vaccines, and can be stored in a refrigerator instead of a freezer.

Trials found it prevented serious illness but was 66% effective overall when moderate cases were included.

The US is the first country in the world to approve the vaccine.

The company has agreed to provide the US with 100 million doses by the end of June. The UK, EU and Canada have also ordered doses, and 500 million doses have also been ordered through the Covax scheme to supply poorer nations.

Results from trials conducted in the US, South Africa and Brazil showed it was more than 85% effective at preventing serious illness, and 66% effective overall when moderate cases were included.

Notably, there were no deaths among participants who had received the vaccine and no hospital admissions after 28 days post-vaccine.

Overall protection was lower in South Africa and Brazil, where virus variants have become dominant, but defence against severe or critical illness was "similarly high".